Introduction: Monstera Siltepecana is an unusual vining foliage plant with attractive leaves that have a silvery sheen between the leaf veins. However, it does not produce basal breaks and hence its use as a potted plant is limited. We felt that stimulating development of basal shoots by growth regulator treatment might enhance its value. With this goal in mind, we treated Monstera Siltepecana with thidiazuron.
Thidiazuron, the active ingredient in a commercial cotton defoliant (Dropp® 50 WP; NOR-AM Chem Co., Wilmington, DE), has been shown to produce cytokinin-like activity in tissue cultures of bean (2). In a previous test with Alocasia (1) thidiazuron stimulated development of many basal buds at the base of treated plants; however, most buds failed to produce leaves or grow out. In addition, shoot and root growth of treated plants were stunted severely at the higher treatment levels.
Materials and Methods: Sixty rooted liners of Monstera Siltepecana, growing in 1-inch plastic cells (72 cells per tray), were potted into 4-inch pots containing VerGro container mix (Verlite Co. Tampa, Fl) on June 8, 1989. Plants were treated with thidiazuron the same day by applying 10 ml (2 teaspoons) of test solution at their base using a syringe. The treatment solutions were made from dilutions of a 100 ppm stock solution (200 mg Dropp® 50 WP/liter = 100 ppm a.i.). Ten plants were treated at each thidiazuron rate of 0, 1, 5, 10, 50 and 100 ppm. Data recorded at 12 weeks after treatment included number of buds longer than 1 cm and fresh weight of shoots and roots.
Results and Discussion: The response of Monstera Siltepecana to thidiazuron treatment was comparable to that observed with Alocasia (1). Treated plants produced several buds greater than 1 cm in length but most buds failed to grow out by termination of the experiment (Table 1). The buds formed at the 50 and 100 ppm treatment levels were abnormal in appearance.
Growth of treated plants was stunted compared to control plants. Root and shoot weights were less at all treatment levels except the 1 ppm rate. At the 50 ppm treatment shoot and root weights were 1/3 and 1/8 of the controls respectively. The small values for root weight at high rates of thidiazuron suggest root loss as all plants were well rooted initially. Avoidance of root damage will be imperative if thidiazuron use as a branching stimulater is to become acceptable commercially. Results from this study indicate that rates tested should not exceed 5 ppm.
Table l. Effect of thidiazuron (Dropp® 50 WP) on plant growth and production of
elongated basal buds in Monstera Siltepecana. Treatments were applied as a 10
ml soil drench to the base of plants in 4-inch pots.
| Thidiazuron concentration (ppm) | Total no. elongated buds | Fresh Weight shoots (g) | Fresh Weight roots (g) | Shoot/ Root Ratio |
| 0 | 0.0 | 31.8 | 10.6 | 3.2 |
| 1 | 0.6 | 35.6 | 10.7 | 3.4 |
| 5 | 6.7 | 30.1 | 7.1 | 4.6 |
| 10 | 16.7 | 26.7 | 4.9 | 6.6 |
| 50 | 11.6 | 10.6 | 1.3 | 8.5 |
| 100 | 3.9 | 6.7 | 0.8 | 10.7 |
| LSD (5%) | 4.8 | 3.9 | 1.9 | 4.1 |
Literature Cited:
1. Henny, R.J. and W.C. Fooshee. 1990. Thidiazuron stimulates basal bud and shoot formation in Alocasia X Chantrieri Andre'. HortScience 25(1):124. 2.
2. Mok, M.C., D.W.S. Mok, D.J. Armstrong, K. Shudo, Y. Isogai and T. Okamoto. Cytokinin activity of N-phenyl-N1-1,2,3-thiadiazol-5-ylurea (Thidiazuron). Phytochemistry 21:1509-1511.